The present invention relates generally to a less current consuming non-contact type 2-channel rotary positioning sensor, and more specifically to a less current consuming non-contact type 2-channel rotary positioning sensor which can accurately measure the magnitude of the magnetism caused by the rotation of a rotating body by eliminating the imbalance of the magnetism that can be generated due to the eccentricity of the rotating body. This invention includes the use of a special geometrical arrangement of sensing bars with two hall elements producing two all most identical linear analog signals. In addition switches are provided by the use of comparator generated switch positions. A microprocessor capable of analog to digital conversion is also included in the present invention to allow digital conversion of the analog signals. The present invention facilates communication with other equipment such as the ECU of a vehicle.
A rotary positioning sensor is conventionally used to apply continuously changing physical changes of a rotating body to electric circuits. Rotary positioning sensors equipped with electric signal output are utilized in various ways in many industries. For example, they are used for the control of the engine throttle valve position for a transport vehicle, rotation angle control of a steering shaft, treading control of an electromagnetic accelerator pedal, positioning control of heavy equipment or farm machines, or on-off measurement of a fluid feed valve.
The methods of measuring rotary positioning include potentiometric sensing, coded disk shaft encoder sensing, hall elements sensing, magneto-resistive sensing, and inductive sensing types. In actual use, it should be possible to operate at temperatures of xe2x88x9240xc2x0 C. to +70xc2x0 C. required by extreme operating conditions of, for example, a commercial vehicle or heavy equipment and to maintain a minimum endurance period of about 5 million operating cycles. In addition the accuracy of any switch position should be kept within an error range of xc2x12% throughout the life of the position sensor together with an endurance exceeding the minimum endurance period of 5 million operation cycles required in working environments of dust and vibration.
Unfortunately the conventional contact potentiometric rotary positioning sensor, which is made of a printed circuit board (hereinafter to be referred to as PCB) or a ceramic board processed with resistance tracks, has drawbacks such as change of electric characteristics due to temperatures and limits to the endurance period and component life due to brush wear. As a result, there are other problems related to the conventional contact resistance potentiometer.
First, with some applications the potentiometer is calibrated to various set points prior to delivery. However experience has shown that after a certain period of operation on a vehicle, the set points have drifted away from specification and exceed a limit value in many cases.
Second, because of the moving wear contact between the electric resistance track and the brush, there is frequently a deterioration in the integrity of the electrical contact between the brush and track. This can make the output signal more vulnerable to the electrical noise caused by the peripheral electric devices and extreme operating conditions (dust, moisture, vibration, temperature). Such electrical noise changes durability and accuracy.
Third, it is impossible to have one design for all applications based on the conventional potentiometer. Design change and further validation of the design is necessary to optimize the conventional potentiometer for different applications which all add to the cost of a product. Examples where major design changes would be needed include the maximum limit to the rated capacity (0.5 watt rated for commercial vehicle, 1.5 watts for heavy equipment) and a change in resistance value (2.5 kW, 5 kW, single track, double track). Each application would require a new design of potentiometer and associated development and tooling costs.
Fourth, in the conventional potentiometer the sensor switch load capacity is restricted to 50 mA or less on average, which has limitations in controlling the load in various control circuits where the potentiometer may be used.
Fifth, a conventional type contact potentiometer with two or more switches built in the sensor is limited by the power supplied from an electromagnetic unit.
It is an object of the present invention to provide a less current consuming non-contact type 2-channel rotary positioning sensor that can accurately provide two independent linear analog measurements of the magnitude of magnetism caused by the rotation of a rotating body. This measurement can be obtained by eliminating the imbalance of magnetism that can occur due to the eccentricity of the rotating body. Two hall elements are used to sense the magnitude of magnetism detected by sensing bars located in different positions.
It is another object of the present invention to facilitate the measurement of the intensity of magnetic force in two different positions either in the same direction or mutually reverse direction according to the positioning of the hall element.
It is yet another object of this invention to provide a less current consuming non-contact type 2-channel rotary positioning sensor that can communicate with a rotating body to quantitatively detect each position of the rotating body. Linear analog measurements are converted into high-resolution digital signals using an analog-to-digital converter.
It is yet another object of this invention to provide a less current consuming non-contact type 2-channel rotary positioning sensor that can eliminate problematic limited life and electric sparks that can occur due to mechanical wear. The present invention also reduces the number and size of parts, and reduces the manufacturing cost. In addition, by using a non-contact type photocoupler in present invention to replace the contact type switch used in conventional type of potentiometer electrical contact damage is eliminated.
It is still yet another object of this invention to provide a less current consuming non-contact type 2-channel rotary positioning sensor that can provide accurate output values with high linearity and low hysterises so that a stable output signal can be guaranteed even during unstable power supply. This avoids electrical noise associated with extreme operating conditions such as temperature change, power source noise, noise due to amplification, electric motor, compressor, dust, moisture, and vibration.
It is further another object of this invention to provide a less current consuming non-contact type 2-channel rotary positioning sensor that can output both analogue and digital signals with the same product and can operate two or more signal switches in various rotary positions. This achieved by the use of a microprocessor (e.g., modification of a microprocessor algorithm) and an analogue comparator circuit.
It is further another object of this invention to provide a less current consuming non-contact type 2-channel rotary positioning sensor with an average power consumption less than 25 mA. In addition the present invention can operate three signal switches having a load capacity of 50 mA or less in various rotary positions and the actual switch value can be altered depend on the application by simple changes to the comparator circuit without the need for redesign or remanufacture associated with normal contact type.
Accordingly, a less current consuming non-contact type 2-channel rotary positioning sensor a housing with a receipt seat formed on the bottom, a cover with sensor mounting holes and through hole for covering the housing, a rotating body whose one end seats on the receipt seat of the housing and whose flange in the middle is joined to the circumference of the through hole of the cover to be supported in a rotatable manner within the housing and whose top end is formed with a coupling slot, a rotary shaft whose one end is coupled with the rotating body by a coupling protuberance inserted into the coupling slot and whose other end is coupled with the rotary object to be measured, a permanent magnet inserted into the base of the rotating body, sensing bars placed in parallel around the base of the rotating body to detect the location of the permanent magnet, and a PCB placed in the housing so as to join with the sensing bars by interposing one or more hall element.